1. Field of the Invention
This invention relates to a method for improving the thermal stability of quaternary ammonium hydroxides present in a hydrocarbon liquid by adding an antioxidant, a metal detergent, a dispersant, or mixtures thereof to the liquid.
2. Background of the Invention
Quaternary ammonium hydroxides have been added to fuels used in internal combustion engines (see U.S. Pat. No. 4,787,916 which discloses that adding a particular class of quaternary ammonium hydroxides to gasoline reduces the octane requirement increase, or ORI). Quaternary ammonium hydroxides have also been added to lubricating oils used in internal combustion engines to reduce ORI and combustion chamber deposits in spark ignition engines, and to reduce oil consumption in diesel engines (see copending patent application Ser. No. 290,401 filed on the same date herewith, now U.S. Pat. No. 4,902,437.
However quaternary ammonium hydroxides will decompose to their corresponding amines when exposed to temperatures above about 40.degree. C. This temperature is readily obtained in an internal combustion engine and is not untypical of liquid storage or delivery systems. As such, the benefits of using these compounds in fuels or lubricating oils will be limited. Therefore, it would be desirable to have available a simple, yet convenient method to improve the thermal stability of quaternary ammonium hydroxides so that the benefits obtained from using these compounds in engine fuels and lubricating oils can be extended.